Safety Status Assessment Of Heavy-duty Railway Bridges Based On Time-varying Reliability

With the development of heavy-haul railway technology,the axle load of heavy-haul trains has increased,and the safety of heavy-haul railway bridges during operation has become a focus of attention.Based on the vehicle-rail-bridge coupling analysis,the safety status of heavy-haul railway bridges based on the time-varying reliability theory have been evaluated in this thesis.The main research contents are as follows:(1)Based on ANSYS,a space model for heavy-duty train-track system-bridge coupling is established,and an improved optimization method for track irregularity excitation is proposed.With C96 heavy-haul train as the load,the dynamic response of the bridge is calculated by numerical simulation,which verified the reliability of the model and the effectiveness of the calculation method.(2)A time-varying model of the cross-section resistance considering the effects of compressive strength of concrete,shrinkage and creep of concrete,and prestress loss is build.The time-varying formula of ballast considering settlement is derived,and the calculation results of the time-varying model of cross-sectional resistance are given with an engineering example.(3)A time-varying reliability assessment method for heavy-haul railway bridges based on response surface method is proposed.Taking bending moment and principal stress of midspan section as reliability indicators,the sensitivity factors of the bridge are analyzed by 2~k factorial design method,and the response surface equation of the reliability index is established by the sensitivity factors,and the time-varying reliability of the bridge is calculated by the improved first-order second-moment method based on the corrosion start time of prestressed steel tendons.The numerical simulation results show that the method can comprehensively consider the influence of time-varying factors and effectively evaluate the state of the bridge.